Viscous Heater, Refrigerant Compressor and Control

ABSTRACT

An HVAC system for a vehicle may include a refrigerant compressor and viscous heater located adjacent to one another and driven by a through-shaft. They may be variable capacity, with the capacities controlled by an HVAC controller to provide the desired HVAC output while staying within a maximum torque limit for an accessory drive.

BACKGROUND OF THE INVENTION

The present application relates to a viscous heater and refrigerant compressor for use in a vehicle heating, ventilation, and air conditioning (HVAC) system.

In a typical automotive vehicle, heat is provided to the passenger compartment by warming the engine coolant, directing some of the engine coolant through a heater core, and warming the air as it flows through the heater core before entering the passenger compartment. While this conventional method of providing heat is still in wide use, both conventional and new types of engines coming into use operate far more efficiently, thus producing less excess heat that is absorbed into the engine coolant. For example, diesel, high efficiency gasoline, and variable displacement engines may not provide sufficient fuel combustion heat rejection into the engine coolant to meet passenger compartment heating or windshield clearing requirements. That is, the long warm-up times for the coolant in these vehicles may be unacceptable to vehicle occupants when operating their vehicles during cold winter months.

As a result, some are looking for ways to provide supplemental heat to make up for the less effective conventional method of heating in order to meet customer comfort requirements. Some supplemental heat sources that have been attempted obtain their energy directly from the fuel in the fuel tank (via external fuel combustion) to provide the additional heat. But these methods somewhat defeat the purpose of employing the high efficiency engines in the first place. Another type of supplemental heater is an electrical resistive heater—but this may require more electric load from the vehicle electrical system than is desirable. Other types of supplemental heaters receive mechanical energy from the engine crankshaft or accessory drive belt. Such heaters may include, for example, hot gas bypass systems that employ the air conditioning circuit, and viscous heaters that apply mechanical energy to the engine coolant to warm it faster. Hot gas bypass systems, though, may add more complexity and cost to the air conditioning system than is desirable.

Employing viscous heaters for providing the supplemental heat offers potential performance and system advantages as compared with these other supplemental heat technologies. But packaging space is tight in the engine compartments of modern vehicles, and this difficulty is compounded by the fact that the viscous heater requires access to the crankshaft or accessory drive belt in order to be driven. This drawback has made employing viscous heaters a significantly less desirable option for providing supplemental heat in vehicles.

SUMMARY OF THE INVENTION

An embodiment contemplates a refrigerant compressor and viscous heater assembly for use with a vehicle HVAC system. The assembly may include a through-shaft, and a drive mechanism rotationally coupled to the through-shaft to provide a drive torque to the through-shaft. A refrigerant compressor operatively engages the through-shaft to be driven by the through-shaft, and a viscous heater is located adjacent to the refrigerant compressor and also operatively engages the through-shaft to be driven by the through-shaft.

An embodiment contemplates an HVAC system for use with a vehicle. The HVAC system may include a refrigerant circuit having a refrigerant compressor, a coolant circuit having a viscous heater located adjacent to the refrigerant compressor, and a through-shaft operatively engaging and providing a drive torque to the refrigerant compressor and the viscous heater. The HVAC system may also include a drive mechanism rotationally coupled to the through-shaft to provide the drive torque to the through-shaft, and an HVAC controller for controlling the refrigerant compressor and the viscous heater.

An embodiment contemplates a method of operating an HVAC system of a vehicle, the method comprising the steps of: driving a refrigerant compressor and a viscous heater, located adjacent to the refrigerant compressor, with a through-shaft; selecting an HVAC mode of operation; adjusting a refrigerant compressing capacity of the refrigerant compressor based at least partially on the selected HVAC mode of operation; and adjusting a heat output capacity of the viscous heater based at least partially on the selected HVAC mode of operation.

An advantage of an embodiment is the ability to provide supplemental heat while minimizing any adverse impact on vehicle packaging. The improved packaging may include shared pulley and support brackets between the refrigerant compressor and viscous heater, as well as a minimal impact to the accessory drive system, which may include a carryover accessory belt or simplified belt routing. This improved packaging may allow for viscous heater based supplemental heating to be employed with a greater number of engines and vehicle platforms. Moreover, this may produce potential weight savings over providing supplemental heating with separate components. And the supplemental heat is provided with minimal increase in electric load and without the need for external combustion of fuel, as is the case with some other types of supplemental heating for vehicles.

An advantage of an embodiment is less cost versus a separate viscous heater or some other types of supplemental heat technologies. The cost savings versus a separate viscous heater may include the avoidance of an extra belt, pulley and brackets, as well as the cost to assemble all of the separate components. Also, if the viscous heater and refrigerant compressor are both variable capacity (i.e., direct drive off of the accessory belt), not only is the cost of a clutch avoided, but there may be weight savings as well. The viscous heater may provide the engine water pump function when directly driven off of the accessory drive belt without an intervening clutch. Again, this can potentially create a cost and weight savings. This weight savings may be further improved should the viscous heater and refrigerant compressor be fully integrated into a single housing.

An advantage of an embodiment is that a control strategy for operating the viscous heater and refrigerant compressor smoothly transitions between cooling and heating needs. This can be accomplished by employing a variable capacity viscous heater and a variable capacity refrigerant compressor in a direct drive arrangement. Such a strategy may also manage the viscous heater and refrigerant compressor to assure that the belt load torque is maintained within an acceptable range for the accessory drive system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a vehicle HVAC system, with coolant and refrigerant circuits.

FIG. 2 is a schematic illustration of a refrigerant compressor and viscous heater assembly, and a controller according to a first embodiment.

FIG. 3 is a schematic illustration similar to FIG. 2, but illustrating a second embodiment.

FIG. 4 is a block diagram of a control strategy that may be employed with the vehicle HVAC system.

DETAILED DESCRIPTION

FIGS. 1-2 illustrate a portion of a vehicle 10, having an engine compartment 12 and a passenger compartment 14. Located within the engine and passenger compartments 12, 14 are a refrigerant circuit 16 and a coolant circuit 18.

The coolant circuit 18 provides a cooling function for an engine 20, and a heating function for the passenger compartment 14 via a heater core 22. The coolant circuit 18 includes a viscous heater 24, which can function as a pump for the coolant in the circuit (if so desired) as well as providing heat to the coolant. The viscous heater 24 is part of a refrigerant compressor and viscous heater assembly 26, which will be discussed in more detail below. Coolant pumped from the viscous heater 24 may be directed through a coolant line 28 to the engine 20. The coolant lines in FIG. 1 are indicated by the dashed lines, with the arrows indicating the direction of flow of the coolant. Upon leaving the engine 20, a coolant line 30 directs the coolant flow to both a coolant line 32 leading to the heater core 22 and to a thermostat valve 34. The thermostat valve 34 may operate in a conventional fashion where the flow of coolant therethrough is blocked until the coolant reaches a desired temperature. Coolant flowing through the thermostat valve 34 is directed, via a coolant line 36, to a radiator 38. Coolant lines 40 and 42 direct coolant from the heater core 22 and the radiator 38, respectively, back to the viscous heater 24, completing the coolant circuit 18.

The refrigerant circuit 16 includes a refrigerant compressor 44, which is mounted adjacent to and axially aligned with the viscous heater 24. A refrigerant line 46 directs refrigerant from the compressor 44 to a condenser 48. The refrigerant lines in FIG. 1 are indicated by the dash-dot-dash lines, with the arrows indicating the direction of flow of the refrigerant. Refrigerant flowing from the condenser 48 enters refrigerant line 50, which directs the refrigerant to an expansion device 52, which may be an orifice tube or a thermal expansion valve. Another refrigerant line 54 directs the refrigerant to an evaporator 56 in an HVAC module 58 in the passenger compartment 14, before directing the refrigerant, via refrigerant line 60, back to the compressor 44, completing the refrigeration circuit 16.

The HVAC module 58 may include a blower 62 for bringing fresh or recirculated air, via a recirculation/fresh air blend door 64, into the module 58 and directing it through the evaporator 56. The air, driven by the blower 62, may selectively be directed through or past the heater core 22 by controlling the position of a heater core blend door 66, before being selectively directed through vents 68 into the passenger compartment 14.

The refrigerant compressor/viscous heater assembly 26 includes a through-shaft 70 that is rotationally coupled to and drives both the viscous heater 24 and the refrigerant compressor 44. A pulley 72 is also rotationally coupled to the through-shaft 70 and provides the torque for driving this shaft 70. While the length of the assembly 26 will increase by the approximate thickness of the viscous heater 24 (relative to a conventional compressor only assembly), with both the viscous heater 24 and refrigerant compressor axially aligned adjacent to each other and driven off of the same shaft 70, a single set of mounting hardware (not shown) can be employed to mount a viscous heater housing 25 and a compressor housing 45 in the engine compartment 12. Also, the single pulley 72 provides the torque for driving both the viscous heater 24 and the refrigerant compressor 44. Thus, this configuration may save both weight and packaging space as compared to a configuration with a supplemental heat source located separate from a refrigerant compressor.

Moreover, if the pulley 72 is connected directly to the shaft 70 (without an intervening clutch) and the refrigerant compressor 44 and viscous heater 24 are variable capacity configurations (which are known in the art), then the coolant may be driven through the coolant circuit 18 by the viscous heater 24. In such an instance, the viscous heater 24 would also function in place of the conventional water pump (not shown) that is employed for pumping coolant through the coolant circuit 18. That is, if no air conditioning and no supplemental heat is required, then the refrigerant pumping capacity of the compressor 44 and the viscous heating capacity of the heater 24 could be reduced to their minimum values, while pumping action of the viscous heater 24 continues pumping the coolant through the coolant circuit 18. The elimination of the clutch and separate water pump may improve packaging and reduce weight over a conventional system.

The pulley 72 engages and is driven by an accessory drive belt 74, which, in turn, is driven off a crankshaft (not shown) of the engine 20. While the mechanism shown for creating torque to drive the through-shaft 70 is shown as the pulley 72 driven by the belt 74 off of the crankshaft (not shown), it could alternatively be a chain and sprocket assembly (not shown) or a gear assembly (not shown) driven off of the crankshaft (or camshaft), or an electric motor (not shown) providing the driving torque to the through-shaft 70. In addition, a fan 76 may be driven off the engine crankshaft or driven by an electric motor, in order to draw air through the radiator 38 and condenser 48.

An HVAC controller 78 communicates with and controls the capacity of the refrigerant compressor 44 and the heat output of the viscous heater 24, (indicated by lines 80 and 82). The level of compressor capacity and heat output affect the driving torque required by the through-shaft 70, which, in turn, determines the torque required at the pulley 72. That is, the sum of the torque of both devices will determine the torque at the pulley 72 at any given moment. So, one function of the controller 78 is to modulate the compressor capacity and heat output, when needed, to assure that the total torque required at the pulley 72 will not exceed accessory drive design limitations.

Another function of the HVAC controller 78 is to monitor system inputs and control the operation of the viscous heater 24 and compressor 44—in response to these inputs—in order to provide cooling, dehumidification, or supplemental heat, as the case may be. The inputs to the HVAC controller 78 (shown in FIG. 2) may include, for example, a temperature set point 86, HVAC mode selection 87, outside ambient air temperature 88, engine speed 89, air conditioning pressure 90, coolant temperature at a viscous heater inlet 91, and engine coolant temperature 92.

With the compressor capacity and heat output being continuously controllable, the HVAC controller 78 operates to assure that smooth torque transitions occur. When maximum cooling is requested, the controller 78 adjusts the viscous heater 24 to near zero heat generation and adjust the refrigerant compressor 44 to its maximum allowable displacement, while controlling the torque induced on the through-shaft 70 to assure that no undesirable torque transitions occur. The same smooth transition occurs for situations where maximum supplemental heat is requested.

FIG. 3 illustrates a second embodiment. This embodiment has many features in common with the first embodiment, so the same element numbers will be used to identify similar elements, but using 100-series numbers. In this embodiment, the controller 178 and inputs 186-192 for controlling the assembly 126 may be the same as in the first embodiment. Also, the pulley 172 and through-shaft 170 may be essentially the same. The significant difference is that the viscous heater housing and compressor housing of the first embodiment are now a combined compressor/viscous heater housing 125 that encloses both the viscous heater 124 and the refrigerant compressor 144. This combined housing 125 may simplify mounting and installation and may reduce the overall weight of the assembly 126.

FIG. 4 illustrates a control strategy for the viscous heater and refrigerant compressor assembly of FIGS. 1 and 2. A desired temperature set point, box 286, is determined based on selections made by the occupant for passenger compartment interior comfort. This temperature set point information, box 286, along with the outside ambient air temperature, box 288, are input to an automatic HVAC control head mode selection, box 287. The HVAC mode needed to meet the occupant request is determined in the mode selection, box 287, which may be, for example, cooling (air conditioning), box 294, heating, box 295, or defogging, box 296.

In the cooling mode, the viscous heater heat output control, box 297, will be controlled to its minimum level of heat input (essentially off), while the refrigerant compressor capacity (displacement), box 298, will be adjusted to provide the required cooling, and may be based upon various inputs, such as, air conditioning pressure, box 290, and engine speed (RPM), box 289. Since the compressor capacity will be a portion of the accessory drive torque load, the level of compressor capacity will be output to calculate total accessory drive torque load, box 299, and adjusted accordingly should the required torque load exceed a maximum acceptable belt load torque for the accessory drive system. Exceeding the belt torque load is less of a concern in the cooling mode than in the heating or defogging modes, because the viscous heater heat output is essentially zero.

In a heating mode, box 295, or defogging mode, box 296, a blend of both viscous heater heat output (for supplemental heat), box 300, and refrigerant compressor operation (for defogging), box 301, may be required simultaneously. If defogging is required, then the refrigerant compressor may be driven at a sufficient capacity to lower the humidity in the air flowing through the HVAC module. Otherwise, the refrigerant compressor capacity may be adjusted to its lowest level (close to zero). The amount of viscous heater heat output required may be based on, for example, the engine coolant temperature, box 292, and the coolant temperature at the viscous heater inlet, box 291. If the coolant temperatures are high enough, then little or no supplemental heating may be required, in which case, the heat output of the viscous heater may be reduced to a low level. If the coolant temperatures are low, then the viscous heater heat output may be adjusted to a high level.

The heat output level and compressor displacement are both output to calculate the accessory drive torque load, box 299, to assure that the maximum belt torque load is not exceeded, and the capacity levels are adjusted to reduce the torque requirements if necessary. Of course, the most likely situation where the requested torque may exceed the maximum belt torque capacity is when defogging is required at the same time that the coolant temperatures are very low so that maximum supplemental heat is desired.

While certain embodiments of the present invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims. 

1. A refrigerant compressor and viscous heater assembly for use with a vehicle HVAC system, the refrigerant compressor and viscous heater assembly comprising: a through-shaft; a drive mechanism rotationally coupled to the through-shaft to provide a drive torque to the through-shaft; a refrigerant compressor operatively engaging the through-shaft to be driven by the through-shaft; and a viscous heater located adjacent to the refrigerant compressor and operatively engaging the through-shaft to be driven by the through-shaft.
 2. The assembly of claim 1 wherein the refrigerant compressor and the viscous heater are contained within an integrated compressor/viscous heater housing.
 3. The assembly of claim 1 wherein the drive mechanism is a pulley rotationally fixed to the through-shaft and an accessory drive belt operatively engaging the pulley to provide a drive torque thereto.
 4. The assembly of claim 1 wherein the refrigerant compressor is a variable capacity compressor and is adapted to have a refrigerant compressing capacity varied by an HVAC controller.
 5. The assembly of claim 4 wherein the viscous heater is a variable heat output viscous heater and is adapted to have a variable heat output varied by the HVAC controller.
 6. The assembly of claim 1 wherein the viscous heater is a variable heat output viscous heater and is adapted to have a variable heat output varied by an HVAC controller.
 7. The assembly of claim 1 wherein the viscous heater is a pump adapted to pump coolant therethrough.
 8. The assembly of claim 1 wherein the viscous heater and the refrigerant compressor are axially aligned.
 9. An HVAC system for use with a vehicle comprising: a refrigerant circuit including a refrigerant compressor; a coolant circuit including a viscous heater located adjacent to the refrigerant compressor; a through-shaft operatively engaging and providing a drive torque to the refrigerant compressor and the viscous heater; a drive mechanism rotationally coupled to the through-shaft to provide the drive torque to the through-shaft; and an HVAC controller for controlling the refrigerant compressor and the viscous heater.
 10. The HVAC system of claim 9 wherein the viscous heater is a variable heat output viscous heater and is adapted to have a variable heat output varied by the HVAC controller.
 11. The HVAC system of claim 9 wherein the refrigerant compressor is a variable capacity compressor and is adapted to have a refrigerant compressing capacity varied by the HVAC controller.
 12. The HVAC system of claim 11 wherein the viscous heater is a variable heat output viscous heater and is adapted to have a variable heat output varied by the HVAC controller.
 13. The HVAC system of claim 9 wherein the refrigerant compressor and the viscous heater are contained within an integrated compressor/viscous heater housing.
 14. The HVAC system of claim 9 wherein the viscous heater is a pump adapted to pump coolant through the coolant circuit.
 15. The HVAC system of claim 9 wherein the HVAC controller is adapted to receive a coolant temperature input and base a heat output control of the viscous heater at least in part on the coolant temperature.
 16. A method of operating an HVAC system of a vehicle, the method comprising the steps of: (a) driving a refrigerant compressor and a viscous heater, located adjacent to the refrigerant compressor, with a through-shaft; (b) selecting an HVAC mode of operation; (c) adjusting a refrigerant compressing capacity of the refrigerant compressor based at least partially on the selected HVAC mode of operation; and (d) adjusting a heat output capacity of the viscous heater based at least partially on the selected HVAC mode of operation.
 17. The method of claim 16 further including the step of (e) rotationally driving the through-shaft with a pulley driven by a belt.
 18. The method of claim 16 wherein step (d) is further defined by adjusting the heat output capacity based at least partially on at least one of an engine coolant temperature and a coolant temperature at an inlet to the viscous heater.
 19. The method of claim 16 wherein steps (c) and (d) are further defined by adjusting the refrigerant compressing capacity and the heat output capacity at least partially on at least one of an outside air temperature and a temperature set point.
 20. The method of claim 16 further including a step of (e) monitoring an accessory drive torque load and adjusting at least one of the refrigerant compressing capacity and the heat output capacity to maintain the accessory drive torque load below a predetermined maximum accessory drive torque load. 